Memory Array TAV Structure With Refractory Nitride Conductors
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Solution Overview
Problem
Existing memory array technologies face challenges in efficiently forming vertically-stacked memory cells with reliable electrical connections and structural integrity, particularly in the formation of through-array vias (TAVs) that ensure consistent conductivity and stability.
Innovation Solution
The method involves forming a memory array with a vertical stack of alternating insulative and conductive tiers, using metal-rich refractory metal nitrides for lower conductor material to create stable through-array vias (TAVs) that directly couple channel-material strings to conductor tiers, ensuring reliable electrical connections and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional through-array via formation methods are used, then manufacturing process is simpler, but electrical conductivity and structural stability of vertically-stacked memory cells deteriorate
Solution Approach 1:
The through-array via formation process is segmented into multiple sequential steps: forming TAV openings through the substrate, depositing a liner layer, filling with conductive material, and planarizing. This segmentation allows each step to be optimized independently, ensuring reliable electrical conductivity while maintaining manageable manufacturing complexity through standardized process modules.
Solution Approach 2:
The liner layer is deposited in advance before filling the TAV openings with conductive material. This preliminary action prepares the via structure with proper adhesion and electrical properties, ensuring reliable conductivity connections between vertically-stacked memory cells before the final conductive material is applied.
2Quantity of substance
If vertically-stacked memory cells are formed with through-array vias, then memory density increases, but structural integrity and connection stability become more difficult to maintain
Solution Approach 1:
The through-array via structure uses composite material composition: a liner layer material (such as tungsten nitride or tantalum nitride) combined with conductive fill material (such as copper or cobalt). This composite structure provides both mechanical strength to maintain structural integrity and electrical conductivity for reliable connections, enabling vertically-stacked memory cells to achieve high density without compromising structural stability.
Solution Approach 2:
The liner layer is applied as a protective cushioning layer before filling the TAV openings. This liner provides mechanical support and stress distribution, preventing structural failure during subsequent processing steps and ensuring long-term connection stability in high-density vertically-stacked memory arrays.
3Reliability
If through-array vias are formed to connect vertically-stacked memory cells, then electrical coupling improves, but manufacturing precision requirements increase
Solution Approach 1:
The TAV openings are formed and lined before final conductive material deposition. This preliminary preparation ensures proper via geometry and surface preparation, reducing variability in electrical coupling. The liner layer also provides a controlled interface that compensates for minor dimensional variations, maintaining reliable electrical connections without requiring extreme manufacturing precision.
Solution Approach 2:
The liner layer material properties (such as deposition thickness, composition, and crystalline structure) are carefully controlled and optimized to provide consistent electrical characteristics. By adjusting these parameters, the process achieves reliable electrical coupling through TAVs while maintaining feasible manufacturing precision requirements for the overall fabrication process.
Data Source
AI summary
A memory array comprising strings of memory cells comprises laterally-spaced memory blocks individually comprising a vertical stack comprising alternating insulative tiers and conductive tiers above a conductor tier. Strings of memory cells comprising channel-material strings extend through the insulative tiers and the conductive tiers. The conductor tier comprises upper conductor material directly above and directly against lower conductor material of different composition from that of the upper conductor material. A through-array-via (TAV) region is included and comprises TAVs individually comprising the upper conductor material, the lower conductor material, and a conducting material that is directly below the conductor tier. The lower conductor material is directly against the conducting material and comprises at least one of (a) and (b), where, (a): a metal-rich refractory metal nitride; and (b): a stoichiometric or non-stoichiometric refractory metal nitride directly above and directly against one of (1), (2), or (3), where: (1): an elemental metal; (2): an alloy of at least two elemental metals; and (3): a metal-rich refractory metal nitride of different composition from that of the stoichiometric or non-stoichiometric refractory metal nitride.. Methods are also disclosed.